V-Sync ON/OFF when FPS < max Hz (+VRR)

[onexo]

This question was most likely answered many times but I can't find the answers...
I have a 240Hz monitor and I play a game that has a 200 FPS limiter. For the lowest input lag, do I use only VRR or VRR + V-Sync + RTSS? V-Sync isn't activated so there shouldn't be any need for it, right?

[jorimt]

This question was most likely answered many times but I can't find the answers...
I have a 240Hz monitor and I play a game that has a 200 FPS limiter. For the lowest input lag, do I use only VRR or VRR + V-Sync + RTSS? V-Sync isn't activated so there shouldn't be any need for it, right?

For V-SYNC ON/OFF with VRR, read the #2 entry here:
https://blurbusters.com/gsync/gsync101- ... ttings/15/

As for an RTSS FPS limit, no you don't need one to further reduce input lag at 240Hz if the game already has a 200 FPS limit (it's already doing that).

[Chief Blur Buster]

Yep....

RTSS is not necessary if the game/emulator/etc is self-limiting in frame rate.

Emulators and some console ports automatically limit to 50fps or 60fps.

For that, you don't need any other capping software. The frame rate limitation is the defacto cap itself.

It's also why some people love G-SYNC for easy low-latency 60fps. Looks like perfect VSYNC ON, but without the lag.

The same principle applies to any other built-in game framerate limitation such as 200fps.

The fallback sync technology (VSYNC ON or VSYNC OFF) never activates until there's a frametime faster than the highest Hz of the VRR range. So VRR+VSYNC OFF and VRR+VSYNC ON is perfectly identical in latency if the game's framerate cap is reliable. Be noted that some caps aim at frametime averaging (letting frametimes fluctuate massively even if the framerate range is wide), rather than prevent ultrashort frametimes.

[TTT]

The fallback sync technology (VSYNC ON or VSYNC OFF) never activates until there's a frametime faster than the highest Hz of the VRR range. So VRR+VSYNC OFF and VRR+VSYNC ON is perfectly identical in latency if the game's framerate cap is reliable. Be noted that some caps aim at frametime averaging (letting frametimes fluctuate massively even if the framerate range is wide), rather than prevent ultrashort frametimes.

I thought there was slight input lag added when enabling Vsync with Gsync?

Doesn't enabling it just stop lower tearing when Gsync is enabled? But with a 240hz monitor its basically impossible to see it anyway.

[Chief Blur Buster]

I thought there was slight input lag added when enabling Vsync with Gsync?

Only if framerates activates it.

There are situations where VSYNC ON is never activated.

Doesn't enabling it just stop lower tearing when Gsync is enabled? But with a 240hz monitor its basically impossible to see it anyway.

There is no tearing with GSYNC + VSYNC OFF with a reliable cap. For example, a 60fps emulator on a 144Hz G-SYNC monitor.

That's because VSYNC OFF is never activated.

The fallback sync technology only activates if the fastest frametime is faster than the fastest refreshtime allowed (top Hz in VRR range). If you control al your frametimes to be within VRR range, then big whoop, the fallback sync technology never activates. Thus no lag or tearing difference.

Now, 141fps at 144Hz is much closer to the limit though. Imperfect framerate caps will have frametimes that jitter around a bit (e.g. 1/130sec, 1/150sec etc, in an attempt to average out at 1/141sec for a 141fps cap. So frametimes aren't exactly equal to each other. So that gives more opportunity for fallback sync technology to activate.

As a rule of thumb:
- The bigger margin the framerate cap below max Hz, the less likely the fallback sync technology activates
- The more reliable (glassfloor) the frame pacing is, the less likely the fallback sync technology activates
- At some point, the fallback sync technology never activates at all.

Which means perfect capping is identical in lag and zero-tearing for GSYNC+VSYNC OFF and for GSYNC+VSYNC ON, because the backup sync technology is never activating. The difference appears if you uncap or reduce margins (cap closer to max Hz, or cap using a less-accurate cap).

[jorimt]

I thought there was slight input lag added when enabling Vsync with Gsync?

Only when the framerate is sustained above the refresh rate, e.g. G-SYNC on + V-SYNC on + 300 FPS @240Hz (etc), does G-SYNC revert to traditional V-SYNC behavior.

The only difference between G-SYNC on + V-SYNC off and G-SYNC on + V-SYNC on is the former can tear within the refresh rate, and the latter can't. And this difference only occurs when A) your framerate is near the max refresh rate or B) there is a frametime spike. Otherwise, they behave identically within the G-SYNC range, input lag levels included.

For complete details on this, read the #2 entry in my Closing FAQ here:
https://blurbusters.com/gsync/gsync101- ... ttings/15/

[TTT]

Thanks

[jorimt]

Thanks

No problem.